Md. Aktaruzzaman

First Report of Web Blight of Rosemary (Rosmarinus officinalis) Caused by Rhizoctonia solani AG-1-IB in Korea

Abstract Herein, we report the first occurrence of web blight of rosemary caused by Rhizoctonia solani AG-1-IB in Gangneung, Gangwon Province, Korea, in August 2014. The leaf tissues of infected rosemary plants were blighted and white mycelial growth was seen on the stems. The fungus was isolated from diseased leaf tissue and cultured on potato dextrose agar for identification. The young hyphae had acute angular branching near the distal septum of the multinucleate cells and mature hyphal branches formed at an approximately 90° angle. This is morphologically identical to R. solani AG-1-IB, as per previous reports. rDNA-ITS sequences of the fungus were homologous to those of R. solani AG-1-IB isolates in the GenBank database with a similarity percentage of 99%, thereby confirming the identity of the causative agent of the disease. Pathogenicity of the fungus in rosemary plants was also confirmed by Koch’s postulates.

First Report of Postharvest Gray Mold Rot on Carrot Caused by Botrytis cinerea in Korea

In February 2014, gray mold rotting symptoms were observed in carrots in cold storage at Gangneung, Gangwon province, Korea. The typical symptom of gray mold rot showed abundant blackish gray mycelia and conidia was observed on the infected root. The pathogen was isolated from infected root and cultured on PDA for further fungal morphological observation and confirming its pathogenicity according to Koch`s postulates. Results of morphological data, pathogenicity test and rDNA internal transcribed spacer (ITS 1 and 4) sequence showed that the postharvest gray mold rot of carrot was caused by Botyrtis cinerea. This is the first report of postharvest gray mold rot on carrot in Korea.

First Report of Potato Stem-End Rot Caused by Fusarium oxysporum in Korea.

Abstract In this study, we identified the causative agent of stem-end rot in potatoes that were grown in Gangwon alpine areas of Korea in 2013. The disease symptoms included appearance of slightly sunken circular lesion with corky rot on the potato surface at the stem-end portion. The fungal species isolated from the infected potatoes were grown on potato dextrose agar and produced white aerial mycelia with dark violet pigments. The conidiophores were branched and monophialidic. The microconidia had ellipsoidal to cylindrical shapes and ranged from 2.6~11.4 × 1.9~3.5 μm in size. The macroconidia ranged from 12.7~24.7 × 2.7~3.6 μm in size and had slightly curved or fusiform shape with 2 to 5 septate. Chlamydospores ranged from 6.1~8.1 × 5.7~8.3 μm in size and were present singly or in pairs. The causal agent of potato stem-end rot was identified as Fusarium oxysporum by morphological characterization and by sequencing the internal transcribed spacer (ITS1 and ITS4) regions of rRNA. Artificial inoculation of the pathogen resulted in development of disease symptoms and the re-isolated pathogen showed characteristics of F. oxysporum. To the best of our knowledge, this is the first study to report that potato stem-end rot is caused by F. oxysporum in Korea.

First Report of Gray Mold Caused by Botrytis cinerea on Strawflower in Korea

Strawflower (Xerochrysum bracteatum) is a flowering plant of the Asteraceae. In July 2016, approximately 10% of inflorescences were observed displaying gray mold symptoms in a private garden in Gangneung, Korea. Initial infection started from the base of inflorescence and gradually moved to the flower spike where it finally collapsed. Lesions expanded rapidly under cool, humid conditions. Diseased tissue was excised and surface sterilized by immersing in 1% sodium hypochlorite (NaOCl) for 1 min, rinsed three times with sterilized distilled water, placed on potato dextrose agar (PDA, Difco) plates, and incubated at 20 ± 2°C for 7 days. The fungus produced gray to grayish brown colonies that sporulated abundantly. The conidia (n = 50) were one-celled, ellipsoid or ovoid, dark brown, and 5.1 to 7.2 × 5.3 to 5.6 μm in vivo, and 5.1 to 10.4 × 5.1 to 7.8 μm in vitro. Conidiophores (n = 20) arose solitary or in groups, straight or flexuous, septate, with an inflated basal cell brown to light brown, and measured ...

First Report of Gray Mold Caused by Botrytis cinerea on Red Raspberry (Rubus idaeus) in Korea

In July 2014, we collected samples of gray mold from red raspberry growing in Gangneung, Gangwon Province, Korea. The disease symptoms were dark brown lesions covered with gray spore masses on the twigs, blossoms, leaves, and fruits of infected plants. We isolated the pathogen from infected leaves and fruits and cultured the fungus on potato dextrose agar. We examined the fungus morphologically and confirmed its pathogenicity according to Koch’s postulates. The results of morphological examinations, pathogenicity tests, and the rDNA sequences of the internal transcribed spacer regions (ITS1 and ITS4) and the nuclear protein-coding gene HSP60 revealed that the causal agent was Botrytis cinerea. This is the first report of gray mold caused by Botrytis cinerea on red raspberry in Korea.

The First Report of Postharvest Stem Rot of Kohlrabi Caused by Sclerotinia sclerotiorum in Korea

Abstract In March 2014, a kohlrabi stem rot sample was collected from the cold storage room of Daegwallyong Horticultural Cooperative, Korea. White and fuzzy mycelial growth was observed on the stem, symptomatic of stem rot disease. The pathogen was isolated from the infected stem and cultured on potato dextrose agar for further fungal morphological observation and to confirm its pathogenicity, according to Koch’s postulates. Morphological data, pathogenicity test results, and rDNA sequences of internal transcribed spacer regions (ITS 1 and 4) showed that the postharvest stem rot of kohlrabi was caused by Sclerotinia sclerotiorum. This is the first report of postharvest stem rot of kohlrabi in Korea.